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Thyroid Uptake and Scan

Definition

A thyroid uptake and scan is a test that uses a radioactive substance and a scanning tool to evaluate the thyroid gland. The scanner picks up where and how much the radioactive substance was taken up by the thyroid. This helps determine the structure, location, size, and activity of the gland.

Reasons for Test

The scan may be ordered to:

  • Determine the cause of an overactive thyroid (hyperthyroidism)
  • Test how well the thyroid is working
  • Determine if a thyroid nodule is functioning (if it is making thyroid hormone)

Thyroid
Goiter
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Possible Complications

Thyroid scans are associated with very few risks. Tell your doctor if you:

  • Have an allergy to medicine or food (including iodine or shellfish)
  • Are (or might be) pregnant or breastfeeding—the test could expose the baby to radiation
  • Take any medicines on a regular basis—some can interfere with test results
  • If you recently had any CAT scans, cardiac catheterizations, or other imaging tests that use contrast dye

What to Expect

Prior to Test

  • You may be asked to avoid certain food (containing iodine) or thyroid medicine before the scan. Some can interfere with the results.
  • Jewelry, dentures, and other metallic objects will be removed.
  • You may be asked not to eat or drink anything after midnight.
  • Your doctor may order some tests to measure the amount of thyroid hormone in your blood.

Description of Test

The procedure is done by a trained technician in the radiology department of a hospital. You will be given a radioactive substance by mouth. Once the substance has had time to collect in the thyroid, the scan begins. You will lie on your back with your head tilted back. You will be asked to lie very still at certain times. A scanner will take pictures of your thyroid from different angles. The camera is not an x-ray machine. It does not expose you to more radiation. You may need to return to the radiology department after 24 hours for additional pictures.

After Test

You will be able to leave after the test is done.

Because of the very low dose of radioactive substance used, the majority of the radioactive substance will leave your body within a day or two. You are not at risk for exposing other people to radiation. You can interact normally with them.

How Long Will It Take?

The scan itself takes about half an hour. The radioactive substance needs time to be absorbed before the scan. You may need to wait 4-6 hours if you take the substance by mouth.

Will It Hurt?

There is no pain associated with a thyroid scan. There may be times when you find it uncomfortable to lie still with your head tilted backward.

Results

The pictures of the scan take about an hour to develop. A radiologist will examine them. Based on the results of the test, further studies or treatment will be recommended.

Call Your Doctor

Call your doctor if you experience any unusual pain or discomfort.

In case of an emergency, call for medical help right away.

Revision Information

  • American Thyroid Association, Inc.

    http://www.thyroid.org

  • Thyroid Foundation of America, Inc.

    http://www.allthyroid.org

  • Public Health Agency of Canada

    http://www.phac-aspc.gc.ca

  • The Thyroid Foundation of Canada

    http://www.thyroid.ca

  • Beers MH, Fletcher AJ, et al. The Merck Manual of Medical Information: Second Home Edition. Whitehouse Station, NJ: Merck Research Laboratories; 2003.

  • Diagnostic tests: thyroid scan. Harvard Medical School Family Health Guide website. Available at: http://www.health.harvard.edu/diagnostic-tests/thyroid-scan.htm. Accessed August 2005.

  • Thyroid-Cancer.net: what is a thyroid scan? Johns Hopkins Thyroid Tumor Center website. Available at: http://www.hopkinsmedicine.org/endocrine/graves/Answer.asp%3FQuestionID%3D14. Accessed August 24, 2005.

  • Thyroid nodule. EBSCO DynaMed website. Available at: https://dynamed.ebscohost.com/about/about-us. Accessed August 24, 2005.

  • Thyroid nodules: symptoms, causes, diagnosis, treatment. American Thyroid Association website. Available at: http://www.thyroid.org/what-are-thyroid-nodules. Accessed August 24, 2005.

  • Thyroid nuclear medicine scan. Dr. Joseph F Smith Medical Library website. Available at: www.chclibrary.org/micromed/00068040.html. Accessed August 24, 2005.

  • Thyroid scan and uptake. RadiologyInfo.org website. Available at: http://www.radiologyinfo.org/en/info.cfm?pg=thyroiduptake. Updated February 2010. Accessed November 19, 2010.